U.S. Pat. No. 7,390,035 discloses a magnetic gate latch having a magnet disposed in a keeper assembly. The magnet attracts a pin in a housing with a handle, when the pin is disposed over the magnet in the keeper assembly, latching the pin in the keeper. A handle or handles are operatively coupled with the pin to retract the pin from the keeper assembly, and a helical coil spring biases the pin to retain the pin within the housing when the handle is in a neutral position, until the gate closes and the pin is positioned over the magnet. The strength of the spring must be matched with the strength of the magnet to allow the pin to be polled toward the magnet when the gate closes but must be strong enough to retain the spring in the housing, when the spring is released from the magnet. It is believed that the relatively weak spring, which remains in compression most of the time, while the gate is latched, is a shortcoming of this design.
U.S. Pat. No. 7,044,511 discloses a magnetic gate latch having a magnet disposed in a housing with a handle that actuates a lever which displaces a pin in relation to the magnet By displacing the pin in relation to the magnet, the handle is capable of unlatching the pin from the housing. When the gate closes, the pin, which is housed in a keeper assembly, is attracted by the magnet into a portion of the housing, latching the gate. The pin is biased by a spring in the keeper assembly and the spring is compressed while the gate is dosed. The spring mu# be weaker than the magnetic force of attraction. Thus, the disclosed magnetic gate latch is susceptible to some of the same mechanical problems as the design in U.S. Pat. No. 7,390,035. When the handle is in the neutral position and the gate closes, the magnet in the housing with a handle attracts the pin and engages the pin in the housing with the handle, latching the gate.
Also, U.S. Pat. No. 5,362,116 discloses a magnet in a keeper assembly, which actuates the latching of a pin that is attractable by the magnet The pin is disposed in a housing with a handle and is biased by spring. Other magnetic gate latches are disclosed in U.S. Pat. Nos. 3,790,197; 5,114,195; International Publ. No. WO 03/067004; and Japanese Abstract for application JP7233666; Pat Publ. JP 3-212589; JP5340149; JP3039580; JP8210001 and JP3191187. None of these references disclose a simple mechanism that can be used with gates that is both functional and robust enough for extended use in the field.